1. Field of the Invention
The present invention relates to a movement detecting device for detecting amount of movement or speed of movement, and especially relates to a detecting device using light transmitting and receiving elements.
2. Description of Related Art
Movement detection devices for generally detecting a movement amount such as distance and/or angle, or speed of movement such as rectilinear velocity (acceleration) and angular velocity (acceleration), are known and take various forms, but those using light transmitting and light receiving elements such as photo-electric elements are widely used in environments where electromagnetic noise frequently occurs.
A typical and well-known example of a movement detection device using a photo-electric element is a rotation speed detection device having a structure as shown in Japanese Patent Provisional Publication No. 59-126913 (1984).
In such a rotation speed detection device, an electric light emitting element and a light receiving element are arranged in opposing relation to one another, therebetween is placed a moving plate having light-transmitting slits, and changes between bright and dark of the light from the light emitting element transmitted through the light-transmitting slits is converted into a voltage at the light receiving element and rotational speeds thereby detected.
As will be appreciated by those skilled in the art, apart from rotation speed it is also possible to detect revolution angle from a base angle position. Further, in a flow regulating valve for regulating fluid flow, the opening angle of the flow regulating valve may be detected in the same manner and used as a control parameter.
In such movement detection devices, it is necessary to arrange a pair of stationary apertured plates, i.e. also provided with light-transmitting slits, between the light emitting element and the light receiving element so that the moving slit plate passes between the stationary plates. By such an expedient better reliability of results is achieved since the light is concentrated to a smaller area between the light transmitter and light receiver.
In such prior art devices, each stationary apertured plate is separately fixed in a support member that holds the light emitting element or the light receiving element respectively by supersonic caulking. That is, the support member for holding the light receiving element or the light emitting element is formed by a thermal plastic synthetic resin, and supersonic caulking is carried out by providing projections at a part of the synthetic resin and inserting the projections into stationary holes formed on the stationary apertured plates.
However, with this kind of fixing structure, the stationary apertured plates tend to become displaced due to the synthetic resin melting during the supersonic caulking procedure. Additionally, the stationary apertured plates tend to move up and down due to vibration during measurements if the projections upon which the plates are located is not completely crushed during caulking. Alignment accuracy of the light-transmitting slits of the stationary apertured plate of the light emitting element and the stationary apertured plate of the light receiving element is thus worsened, and accurate signals may not be detected. Detection accuracy is also worsened if the stationary apertured plates move away from the associated light emitting element or the light receiving element so that the light becomes defused, thereby causing a decrease in light intensity, resulting in accurate signals not being detected.
Furthermore, in the prior art the support member that holds the light receiving element and that which holds the light emitting element are formed in separate structures to facilitate the supersonic caulking. In assembly there is a tendency for displacement between both support members since both the support members are joined together by screws. This also diminishes alignment accuracy of the light-transmitting slits of the stationary apertured plates, so accurate signals can not be detected. In this respect, when alignment accuracy of the light-transmitting slits is worsened, although signals may be generated, the controller which receives the signals often determines there to be a no signal condition which leads to serious misoperation and may cause problems in the equipment designed to use the controller's output signals.
An object of this invention is to provide a movement detection device with improved alignment accuracy of the apertures in the stationary apertured plates associated with the light emitting element and the light receiving element respectively.
Another object of the present invention is to provide a movement detection device which firmly fixes the stationary slit plates with an improved alignment.
Still another object of the present invention is to provide a movement detection device in which the stationary slit plates with an increased alignment and the holding part for holding the light receiving and the light emitting elements are firmly and accurately assembled.
Still another object of the present invention is to provide an internal combustion engine or fluid regulating flow detector having an improved structure for signal resolution performance.